1. Field of the Invention
This invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device wherein a pair of radiating terminals and a plurality of lead terminals are formed from a single lead frame.
2. Description of the Related Art
Conventionally, semiconductor devices such as an LSI (Large Scale Integrated Circuit) and a transistor are utilized in various electronic apparatus.
In such apparatus as just mentioned, a pellet comprising a semiconductor circuit is encapsulated in a resin member, and a plurality of lead terminals each formed from an elongated conductive plate are provided on the opposite sides of the resin member. Since those lead terminals are connected to connection pads of the pellet in the inside of the resin member, if the semiconductor device is mounted on a circuit board and the lead terminals are connected to signal lines, then various signals can be inputted to and outputted from the pellet.
While such semiconductor devices are utilized to various applications, for example, a semiconductor device for use with a portable telephone set consumes a large amount of power, and consequently, a pellet of the semiconductor device generates a large amount of heat. Therefore, the generated heat of the pellet must be radiated efficiently.
A conventional example of a semiconductor device which solves the subject just described is described below with reference to FIG. 1.
In integrated circuit device 1 which is a semiconductor device shown as an example here, a pellet of an integrated circuit formed from a semiconductor circuit is mounted on a radiating plate in the form of an island (not shown), and a pair of radiating terminals 2 having a comparatively large width are provided on the opposite left and right sides of the radiating plate.
A plurality of lead terminals 3 having a comparatively small width are arranged at positions forwardly and rearwardly of and adjacent to radiating terminals 2. Lead terminals 3 are connected to connection pads of the pellet by bonding wires (not shown).
Since the pellet, the radiating plate, the bonding wires, inner portions of radiating terminals 2 and inner portions of lead terminals 3 are encapsulated in resin member 4, outer portions 5 and 6 of terminals 2 and 3 are provided projectingly on the left and right side faces of resin member 4.
Outer portions 5 and 6 of terminals 2 and 3 are bent downwardly, and each of radiating terminals 2 has a hole 7 in the form of a slit formed at the bent portion thereof.
When integrated circuit device 1 having such a construction as described above is to be mounted onto an upper surface of a circuit board, the plurality of lead terminals 3 of integrated circuit device 1 are connected to a plurality of signal lines of the circuit board by solder, and the pair of radiating terminals 2 are connected to conductor patterns such as grounding lines of the circuit board.
Thus, the pellet can input and output various information signals to and from the signal lines of the circuit board, and when the pellet generates heat, the heat is radiated from radiating terminals 2.
A method of manufacturing integrated circuit device 1 having such a construction as described above is described briefly below with reference to FIGS. 2 and 3.
First, lead frame 11 is formed by etching a thin metal plate as seen in FIG. 2. On this lead frame 11, a plurality of frame patterns 12 of integrated circuit devices 1 are arranged in rows and columns, and radiating plate 13 is positioned at the center of one frame pattern 12.
A pair of radiating terminals 2 having a comparatively large width are provided on the opposite left and right sides of radiating plate 13. A plurality of lead terminals 3 having a comparatively small width are arranged on the opposite front and rear sides, which are upper and lower sides in FIG. 2, of radiating terminals 2.
Intermediate portions of terminals 2 and 3 are connected to each other by a plurality of tie bars 14. Outer end portions of terminals 2 and 3 are connected to outer frame portion 16 of frame pattern 12 by suspending pins 15.
Inner portions 17 of lead terminals 3 are formed such that they are directed radially toward the center of radiating plate 13. Inner portions 18 of radiating terminals 2 are formed integrally with radiating plate 13.
Holes 7 each in the form of a slit are formed at portions of outer portions 5 of radiating terminals 2 at which radiating terminals 2 are to be bent later.
A pellet comprising a semiconductor circuit is placed onto an upper face of radiating plate 13 of lead frame 11 formed in such a manner as described above, and a plurality of connection pads of the pellet and the plurality of lead terminals 3 are individually connected to each other with bonding wires (not shown).
Lead frame 11 on which the pellet and the bonding wires are mounted integrally in this manner is placed into a cavity of a set of mutually removable metal molds such that it is held at outer portions 5 and 6 of radiating terminals 2 and 3 thereof by and between the metal molds, and in this state, molten resin is filled into the cavity of the metal molds and is then left so as to be solidified to form resin member 4.
Then, as shown in FIG. 3, tie bars 14 and suspending pins 15 of lead frame 11 which are exposed to the outside from resin member 4 are cut away by punches 19 to 21 so that outer portions 5 and 6 of radiating terminals 2 and lead terminals 3 are separated from each other, and outer portions 5 and 6 are bent downwardly, thereby completing integrated circuit device 1.
When outer portions 5 and 6 of terminals 2 and 3 are bent in this manner, although radiating terminals 2 generally have a comparatively large width, since holes 7 are formed at the bent portions of radiating terminals 2, radiating terminals 2 can be bent readily similarly to lead terminals 3 having a comparatively small width.
However, since radiating terminals 2 and lead terminals 3 have different widths, punches 19 to 20 for cutting away tie bars 14 and suspending pins 15 cannot be arranged in an equal pitch.
Where punches 19 and 20 cannot be arranged in an equal pitch, operations for setting punches 19 and 20 to a press machine (not shown) are cumbersome, and also the universality of thus set punches 19 and 20 is low.
Further, in order to cut away suspending pins 15 of lead terminals 3 having a comparatively small width and suspending pins 15 of radiating terminals 2 having a comparatively large width, punches 20 having a comparatively small width and punches 21 having a comparatively large width are required. In other words, since a plurality of kinds of punches 20 and 21 having different widths are required, the productivity of integrated circuit device 1 is deteriorated thereby.